Apparatus and method for on-line decomposition of hydrogen peroxide solution in fabrication of semiconductor device

ABSTRACT

An apparatus and method for on-line decomposition of a hydrogen peroxide solution, for use in fabricating a semiconductor device, includes a membrane tube having a porous plug inserted in each end, with the porous plugs defining a space where a platinum catalyst is disposed. A first coupling tube is inserted into one end of the membrane tube to supply a hydrogen peroxide sample to the membrane tube. The hydrogen peroxide contained in hydrogen peroxide sample is decomposed into water and oxygen gas according to an action of the platinum catalyst. A second coupling tube is inserted into a second end of the membrane tube to discharge a diluted hydrogen peroxide solution to an analytical instrument, where the decomposed hydrogen peroxide solution is analyzed on-line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and a method for on-linedecomposition of a hydrogen peroxide solution for use in the fabricationof a semiconductor device and, more particularly, to an apparatus and amethod for decomposing the hydrogen peroxide solution on-line and theninjecting the decomposed products into an analytical instrument tothereby analyze the micro contaminants in the hydrogen peroxidesolution.

2. Discussion of the Related Art

As the size of a semiconductor device is reduced further and further,and thus becomes more densely integrated, micro contaminants existing inthe constituent layers of the semiconductor device exhibit a greatereffect on the device characteristics. Consequently, there is acontinuing emphasis to remove the micro contaminants throughout thefabrication process of the semiconductor device.

Generally, a wet cleaning process is the most widely used procedure toreduce or eliminate semiconductor wafer contamination. However, thechemicals used in the wet cleaning process must also have a high degreeof purity so as to prevent a wafer from being re-contaminated by the wetcleaning process itself. Therefore, it is necessary to perform aquantitative and qualitative analysis of the micro contaminantscontained in the chemicals prior to their use. The micro contaminantscan include heavy metals such as iron (Fe), aluminum (Al), copper (Cu),and the like, and ions of sodium (Na⁺), ammonium (NH₄ ⁺), nitrate (NO₃⁻), chloride (Cl⁻), and the like. In order to analyze thesecontaminants, analytical apparatus and methods are used, for example, agraphite reactor atomic absorption spectrometer (GFAAS), an inducedcoupling plasma mass spectroscope (ICP-MS) and an ion-exchangechromatograpy (IC).

Hydrogen peroxide solution is one chemical that is widely used in wetcleaning processes for semiconductor devices. However, the hydrogenperoxide readily oxidizes, making it difficult for the analyzer toperform a successful analysis because the oxidation may cause damage tothe analytical instruments. In addition, the oxidation could also resultin changes in viscosity of the cleaning solution, and the generation ofbubbles when analyzing a highly concentrated hydrogen peroxide solutionin the above analytical instruments.

Accordingly, to perform an efficient analysis of the hydrogen peroxidesolution in an analytical instrument, it is necessary to reduce theconcentration of hydrogen peroxide. Different methods are used to reducethe concentration of the hydrogen peroxide. In a so-called dilutionmethod, the hydrogen peroxide solution is diluted with distilled water.In another so-called decomposition method, the hydrogen peroxidecontained in the hydrogen peroxide solution is decomposed into water andoxygen gas.

The dilution method is easy and simple to carry out, but it has adisadvantage in that the detection capacity of the instrument maydeteriorate as a result of the frequent dilution of the sample.Accordingly, it is not suitable for a method of reducing theconcentration of hydrogen peroxide which requires a detection capacityfor contaminants on the order of a hundred parts per trillion (ppt) andless.

In an attempt to solve this problem, another technique has beendeveloped whereby the hydrogen peroxide solution is concentrated in ananalytical column before an analysis is carried out. In this technique,the hydrogen peroxide solution is first diluted to a designated point sothat it does not damage the analytical column, and is then againconcentrated on line in the column so as to minimize the deteriorationof detection sensitivity. But, this method is not applicable toperforming infinitesimal quantitative analysis because it requiresanother apparatus and additional concentration steps. As a result, theanalysis time is prolonged and the possible contamination of the sampleis increased due to the extended sample flow path.

On the other hand, a decomposition method, which is carried out using aplatinum catalyst, has merit in that the detection capacity is notlowered because there is no need to dilute the sample. In such aplatinum catalyst decomposition method, a platinum wire or platinum netis used as a heterogeneous catalyst in the hydrogen peroxide solution.The platinum catalyst can be reused because the catalyst does notdissolve in the hydrogen peroxide solution, and an aqueous solution isproduced according to the decomposition of hydrogen peroxide.

However, this method also suffers some drawbacks in that it takes a longtime to decompose the sample, raising other possible contaminationproblems during the decomposition. Also, the contaminants containedwithin the sample may be chemically changed due to the heat generated bythe decomposition of the hydrogen peroxide solution.

In another decomposition method for hydrogen peroxide using ultraviolet(UV) rays, the hydrogen peroxide solution contained in a quartzcontainer is irradiated by the ultraviolet (UV) rays. One benefit of theUV method is that there is no need to add any materials to the hydrogenperoxide solution. However, the UV method also presents problems,perhaps more serious than the platinum catalyst decomposition method, inthat it takes a much longer time for decomposition and causes muchgreater chemical changes in the contaminants in the solution.

An additional disadvantage of both of the above-described platinumcatalyst and UV decomposition methods is that each is carried out in abatch process, and therefore the apparatus for decomposition cannot beconnected on-line to the analytical instruments. As such, it isdifficult to perform an on-line, real-time automatic analysis of thesample.

Accordingly, a need exists for an on-line decomposition apparatus andmethod for reducing the concentration of hydrogen peroxide contained inthe hydrogen peroxide solution so as to perform an on-line, real-timeautomatic analysis of micro contaminants in an analytical instrument.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an apparatus andmethod for on-line decomposition of a hydrogen peroxide solution for usein the fabrication of semiconductor device that substantially overcomesone or more of the problems due to limitations and disadvantages of therelated art.

An object of the present invention is to provide an apparatus foron-line decomposition of a hydrogen peroxide solution for use in thefabrication of semiconductor device, which reduces the concentration ofhydrogen peroxide contained in the hydrogen peroxide solution so asallow for an on-line real time automatic analysis of micro contaminantsin an analytical instrument.

Another object of the present invention is to provide a method ofon-line decomposition of hydrogen peroxide solution using the aboveapparatus.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, there isprovided an apparatus for on-line decomposition of a hydrogen peroxidesolution for use in fabricating a semiconductor device, comprising: amembrane tube having first and second ends; a porous plug inserted ineach of the first and second ends, the porous plugs being separated by adesignated distance, thereby defining a space within the membrane tube;a platinum catalyst disposed in the space within the membrane tube; anouter glass tube enclosing the membrane tube; a first coupling tubeinserted into the first end of the membrane tube so as to supply ahydrogen peroxide sample to the membrane tube; and a second couplingtube inserted into the second end of the membrane tube so as todischarge a decomposed hydrogen peroxide solution which passes throughthe platinum catalyst disposed in the membrane tube, said decomposedhydrogen peroxide solution being analyzed on-line.

The first coupling tube is connected to a sample-supply pump for pumpingthe sample from a sample container and thereafter supplying the samplethrough the first coupling tube, so as to make it easy to supply thesample.

The membrane tube, which is permeable to gas and impermeable to liquid,may be made of porous poly tetrafluoroethylene (PTFE), porous polyvinylidenefluoride (PVDF), or porous poly propylene (PP). The porousplugs for fixing the platinum catalyst inside the membrane tube may bemade of TEFLON™ or poly propylene. The first and second coupling tubesmay also be made of TEFLON™ materials

One end of the outer glass tube is closed in relation to the membranetube and the other end of the outer glass tube is opened in relation tothe membrane tube, so that it is easy for the water vapor and the oxygengas generated during the decomposition of hydrogen peroxide solution toexit to the atmosphere via the open end.

The platinum catalyst may take on many forms, including platinum powder,a platinum-coated glass bead, a platinum-coated silica gel, a highlypure platinum wire, a platinum-coated nichrome wire, and 5% platinumactive carbon powder.

In another aspect, the present invention provides for a method ofon-line decomposition of hydrogen peroxide solution for use infabricating a semiconductor device, said method comprising the steps of:supplying a sample of hydrogen peroxide solution, from a samplecontainer via a first coupling tube, to a membrane tube having aplatinum catalyst disposed therein; decomposing hydrogen peroxidecontained in the hydrogen peroxide solution into water and oxygen gasaccording to an action of the platinum catalyst; injecting thedecomposed hydrogen peroxide solution from the membrane tube into ananalytical instrument via a sample injector; and analyzing thedecomposed hydrogen peroxide solution on-line.

The oxygen gas generated as a result of decomposition of the hydrogenperoxide solution is immediately discharged through the membrane tube,so that the concentration of hydrogen peroxide in the hydrogen peroxidesolution can be reduced. An on-line automatic analysis is carried outwhen the decomposed sample is injected into the analytical instrument.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

The foregoing and other objects, aspects and advantages will be betterunderstood from the following detailed description of a preferredembodiment of the invention with reference to the drawings, in which:

FIG. 1 is a sectional view showing an apparatus for on-linedecomposition of a hydrogen peroxide solution according to an embodimentof the present invention; and

FIG. 2 is a schematic view of the on-line connection of the apparatus inFIG. 1 between a sample container and an analytical instrument.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Reference will now be made in detail to a preferred embodiment of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Referring to FIGS. 1 and 2, the on-line decomposition apparatus 10includes a first coupling tube 22 connected at one end to asample-supply pump 40, with the other end of the first coupling tube 22being inserted into one end of a membrane tube 12 contained within theapparatus 10. TEFLON™ tape is used to seal the connection between thefirst coupling tube 22 and the membrane tube 12. When TEFLON™ is used inthis specification, it refers to a commercially-available type of thepolymer tetrafluoroethelyne. However, any substance exhibiting similarproperties, such as a porous poly tetrafluoroethelyne (PTFE), a porouspoly vinylidenefluoride (PVDF), or porous poly propylene (PP) may beused in place of TEFLON™.

A second coupling tube 24 is connected at one end to a sample injector50, with the other end of the second coupling tube 24 being insertedinto a second end of the membrane tube 12 contained within the apparatus10. TEFLON™ tape is used to seal the connection between the secondcoupling tube 24 and the membrane tube 12. The first and second couplingtubes 22, 24 may be made of teflon, for example.

At the locations on the inside of the membrane tube 12 where the firstand second coupling tubes 22, 24 are inserted, plugs 14, 14' areprovided. The plugs 14, 14' are in the form of disks which are made ofporous polymer materials such as TEFLON™ or poly propylene, for example.A platinum catalyst 16 is disposed between the two plugs 14, 14'.

The membrane tube 12 is enclosed by a glass tube 18 having a largerdiameter so as to exclude possible contamination from the outside air.The end of the glass tube 18 closest to the sample-supply pump 40contacts and closes around the membrane tube 12, while the other end ofthe glass tube 18 closest to the sample injector 50 is opened, that is,it does not contact the membrane tube 12, so as to allow gas from theinside of the membrane tube 12 to effuse to the outside.

As shown in FIG. 2, in the apparatus for on-line decomposition ofhydrogen peroxide solution according to the present invention, the firstcoupling tube 22 is connected to a sample container 30 through thesample-supply pump 40 and to an analytical instrument 60 through thesample injector 50. In a preferred embodiment of the present invention,the analytical instrument used is an ion-exchange chromatography (IC),for example, Model No. ASRS-I made by Dionex Co. of Sunnyvale, Calif.

The membrane tube 12 is preferably made of porous TEFLON™ materials,which makes it possible to change the length of the tube. Also, theporous TEFLON™ materials allow the membrane tube 12 to separate gas fromliquid because the TEFLON™ materials allow gas to flow in and out butthey prevent liquid from being transmitted. In other words, the membranetube 12 is permeable to gas and impermeable to liquid. Moreparticularly, the membrane tube 12 may be made of, for example, any ofthe following: porous poly tetrafluoroethylene (PTFE), porous polyvinylidene fluoride (PVDF) or porous poly propylene (PP).

The platinum catalyst 16 in the membrane tube 12 may be, for example, aplatinum powder, a highly pure platinum wire, a platinum-coated nichromewire, a platinum-coated glass bead, a platinum-coated silica gel, orsimilar material.

The apparatus and method for on-line decomposition of a hydrogenperoxide solution according to the present invention operates asfollows. The hydrogen peroxide solution is pumped by the sample-supplypump 40 from the sample container 30 through the first coupling tube 22,through the porous plug 14, and then into the membrane tube 12 (in thedirection of A in FIG. 1). Hydrogen peroxide contained in the hydrogenperoxide solution undergoes a rapid decomposition into water and oxygengas by the action of the platinum catalyst 16 when passing through themembrane tube 12, so that the hydrogen peroxide solution is diluted.During this process, the oxygen gas that is generated by thedecomposition passes through the porous membrane tube 12 and isdischarged into the air through the open end of the glass tube 18 (inthe direction of C in FIG. 1). Then, the decomposed or diluted hydrogenperoxide solution is injected into the analytical instrument through thesample injector 50 (in the direction of B in FIG. 1) for an on-line,real-time analysis.

A performance test was carried out in the apparatus for on-linedecomposition of hydrogen peroxide solution according to the presentinvention, where platinum catalysts 16 of various forms were disposed inthe membrane tube 12 thereof. For the test, the first coupling tube 22was connected to the membrane tube 12 and to the peristalticsample-supply pump 40. A concentrated hydrogen peroxide solution wasthen injected into the on-line decomposition apparatus. The resultingsolution was collected and the remaining hydrogen peroxide which was notdecomposed was titrated with KMnO₄ so as to measure the decompositiondegree. The results are shown in Table 1.

                  TABLE 1    ______________________________________    Performance Test Using Different Platinum Catalysts                       Flux Velocity                                  Decomposition    Forms of Platinum Catalyst                       (mL/min)   Degree    ______________________________________    Screw-Shaped Platinum Wire                       0.69       46.0    Platinum-Coated Glass Beads                       0.20       65.3    5% Platinum Active Carbon Powder                       0.20       >99.9    Platinum-Plated Nichrome Wire                       0.21       >99.9    Platinum Wire      0.29       99.6    ______________________________________

As shown in Table 1, the decomposition degree is strongly affected bythe materials and the forms of the platinum catalyst employed. Inparticular, the 5% platinum active carbon powder, the platinum-platednichrome wire and the platinum wire all achieve a high decompositiondegree.

According to the present invention, many samples of hydrogen peroxidecan be rapidly processed as a result of the automated, real-time,on-line decomposition apparatus and method. In addition, the stabilityand reliability of wet cleaning processes are ensured since the purityof the hydrogen peroxide solution is immediately certified and theefficiency in quality control of chemicals is promoted.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the apparatus and methoddescribed above without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention cover themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

What is claimed is:
 1. An apparatus for on-line decomposition of ahydrogen peroxide solution for use in fabricating a semiconductordevice, comprising:a sample container for containing a hydrogen peroxidesolution sample to be analyzed; an analytical instrument for theanalysis of the hydrogen peroxide solution sample; a membrane tubehaving first and second ends, the membrane tube being permeable to gasand impermeable to liquid; a porous plug inserted in each of said firstand second ends, said porous plugs being separated by a designateddistance, thereby defining a space within said membrane tube; a platinumcatalyst disposed in said space within said membrane tube; an outerglass tube enclosing the membrane tube; a first coupling tube connectedto the sample container and inserted into said first end of saidmembrane tube so as to supply a hydrogen peroxide sample from saidsample container to said membrane tube; a sample supply-pump installedin the first coupling tube so as to supply the hydrogen peroxide sample;a second coupling tube inserted into said second end of said membranetube so as to discharge a decomposed hydrogen peroxide solution whichpasses through said platinum catalyst disposed in said membrane tube;and a sample injector connected to the second coupling tube forinjecting the decomposed hydrogen peroxide solution into the analyticalinstrument for on-line analysis.
 2. The apparatus as defined in claim 1,wherein said membrane tube is manufactured of a material selected fromthe group consisting of porous poly tetrafluoroethylene (PTFE), porouspoly vinylidenefluoride (PVDF) and porous poly propylene (PP).
 3. Theapparatus as defined in claim 1, wherein said porous plugs are made ofone of teflon and poly propylene.
 4. The apparatus as defined in claim1, further comprising teflon tape for sealing the connection between thefirst end of the membrane tube and the first coupling tube, and theconnection between the second end of the membrane tube and the secondcoupling tube.
 5. The apparatus as defined in claim 1, wherein saidfirst and second coupling tubes are made of teflon materials.
 6. Theapparatus as defined in claim 1, wherein one end of said outer glasstube is closed in relation to said membrane tube and another end of saidouter glass tube is open in relation to said membrane tube.
 7. Theapparatus as defined in claim 1, wherein said platinum catalyst isselected from the group consisting of platinum powder, a platinum-coatedglass bead, and a platinum-coated silica gel.
 8. The apparatus asdefined in claim 1, wherein said platinum catalyst is selected from thegroup consisting of highly pure platinum wire, a platinum-coatednichrome wire, and 5% by weight platinum active carbon powder.